Refrigerant compressor

ABSTRACT

A refrigerant compressor according to the present invention is configured that at least one member constituting an electric element and a compression element is made of a rubber material. This rubber material is nitrile rubber, in which: Condition 1: bound acrylonitrile content is within a range of 35 to 51% by weight; Condition 2: organic compound having carbon atom, which is capable of creating double bond with sulfur atom, nitrogen atom or carbon atom and is also capable of creating single bond with sulfur atom or nitrogen atom, is not used as a vulcanizing accelerator in the process for creating cross-linkage; and Condition 3: no phthalic ester is contained.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a refrigerant compressor, which is employed for a refrigerator, an air conditioner and the like.

2. Description of the Related Art

In recent years, improvement in efficiency of sealed refrigerant compressors has progressed. This is primarily for the purpose of reducing consumption of fossil fuels, in view of the protection of the global environment. A technology for achieving improvement in a refrigerating capability by decreasing the temperature of a refrigerant in suction is known as one of approaches for improving the efficiency. In this technology, a member made of an elastomer is generally employed for a member provided in a refrigerant compressor (referred to as “internal member” for the convenience in the description).

For example, Patent Literature 1: Japanese Laid-Open Patent Application Publication No. 2008-223605, or Patent Literature 2: Japanese Laid-Open Patent Application Publication No. 2008-215194, discloses a technology for providing a guide made of a rubber between a suction pipe for introducing a refrigerant into a sealed container and a suction muffler (or a silencer) provided inside the sealed container. This guide made of the rubber corresponds to the above-described internal member, and nitrile rubber is preferably employed as disclosed in, for example, Patent Literature 1.

Meanwhile, the internal member made of the nitrile rubber ordinarily contains phthalic ester as a plasticizer and the like for the nitrile rubber. It is pointed out in recent years that phthalic ester has a potential to adversely affect human bodies and the natural environment.

Thus, an alternative internal member may be produced by employing nitrile rubber containing no phthalic ester, but this may cause a fear for reducing a quality of this internal member.

For example, typical refrigerants employed in the refrigerant compressor include hydrocarbon-based refrigerants such as R600a and the like, or so-called chlorofluorocarbon (CFC) alternatives such as hydrofluorocarbon (HFC) and the like. In addition, oil-based materials such as a lubricating oil and the like are also employed in the sealed container. If these refrigerants or oil-based materials, or mixtures thereof become in contact with the phthalic-ester-free nitrile rubber, a deposit may be generated or a blister may be generated on the surface of the nitrile rubber. These surface abnormalities cause deterioration in the quality of the internal member.

SUMMARY OF THE INVENTION

The present invention is made in order to solve such a problem, and it is an object of the present invention to provide a sealed refrigerant compressor comprising a member formed by employing a phthalic-ester-free nitrile rubber (internal member) therein, which can suppress deterioration in the quality of this member and achieve enhanced reliability.

According to the present invention, there is provided a refrigerant compressor which reserves a lubricating oil having a viscosity of VG3 to VG22 in a sealed container and accommodates an electric element and a compression element that is actuated by the electric element to compress the refrigerant, wherein at least one of members (internal members) constituting said electric element and members (internal members) constituting said compression element is made of a rubber material, and wherein the rubber material is nitrile rubber, in which: bound acrylonitrile content is within a range of 35 to 51% by weight; organic compound having carbon atom, which is capable of creating double bond with sulfur atom, nitrogen atom or carbon atom and is also capable of creating single bond with sulfur atom or nitrogen atom, is not used as a vulcanizing accelerator in a process for creating cross-linkage; and no phthalic ester is contained.

In accordance with this configuration, the nitrile rubber satisfies: using none of the aforementioned kind of vulcanizing accelerator (Condition 1); containing no phthalic ester (Condition 2); and in addition, providing the bound acrylonitrile content within the aforementioned range (Condition 3). Therefore, deterioration in the quality of the internal member is suppressed even if the internal member is in contact with, for example, an HFC-based refrigerant. As a result, reliability of the sealed refrigerant compressor can be further enhanced.

In the aforementioned refrigerant compressor, the aforementioned nitrile rubber may be vulcanized by peroxide vulcanization.

In accordance with this configuration, the nitrile rubber further satisfies a condition of conducting the peroxide vulcanization (Condition 4). Therefore, deterioration in the quality of the internal member is suppressed even if the internal member is in contact with, for example, a hydrocarbon-based refrigerant. As a result, reliability of the sealed refrigerant compressor can be further enhanced.

The above objects and other objects, advantages and features of the present invention will be more apparent from the following description of certain preferred embodiments taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view, illustrating a typical example of a configuration of a refrigerant compressor according to the present invention.

FIG. 2 is a longitudinal sectional view, illustrating a section of the refrigerant compressor shown in FIG. 1, viewed from a center axis direction of a suction pipe.

FIG. 3 is a graph showing relations between contents of bound acrylonitrile and glass transition temperature of nitrile rubber.

FIG. 4 is an infrared (IR) spectrum representing results of Comparative example 1 of the present invention, showing the results of analysis for deposits generated on the surfaces of samples of internal members employing the phthalic-ester-free nitrile rubber with Fourier transform infrared spectrophotometer (FT-IR).

FIG. 5 is an IR spectrum representing results of the Comparative example 2 of the present invention, showing the results of analysis for deposits generated on the surfaces of samples of the internal members employing the phthalic-ester-free nitrile rubber with FT-IR.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the present invention, there is provided a refrigerant compressor which reserves a lubricating oil having a viscosity of VG3 to VG22 in a sealed container and accommodates an electric element and a compression element that is actuated by the electric element to compress the refrigerant, wherein at least one of members (internal members) constituting said electric element and members (internal members) constituting said compression element is made of a rubber material, and wherein the rubber material is nitrile rubber, in which: bound acrylonitrile content is within a range of 35 to 51% by weight; organic compound having carbon atom, which is capable of creating double bond with sulfur atom, nitrogen atom or carbon atom and is also capable of creating single bond with sulfur atom or nitrogen atom, is not used as a vulcanizing accelerator in a process for creating cross-linkage; and no phthalic ester is contained.

In accordance with this configuration, the nitrile rubber satisfies: Condition 1: using none of the aforementioned kind of vulcanizing accelerator; Condition 2: containing no phthalic ester; and in addition, Condition 3: providing the bound acrylonitrile content within the aforementioned range. Therefore, deterioration in the quality of the internal member is suppressed even if the internal member is in contact with, for example, an HFC-based refrigerant. As a result, reliability of the sealed refrigerant compressor can be further enhanced.

In the refrigerant compressor having the aforementioned configuration, the aforementioned nitrile rubber may exhibit Mooney viscosity ML₁₊₄ at 100 degrees C. of within a range from 50 to 150 and a hardness of within a range from 55 degrees to 80 degrees.

In accordance with this configuration, since the nitrile rubber satisfies the additional conditions related to the aforementioned range of the Mooney viscosity and the aforementioned range of the hardness, easy manufacture and installation are achieved, depending on the kind of the internal member. Hence, this provides further enhanced reliability of the refrigerant compressor.

Further, in the refrigerant compressor having the aforementioned configuration, the aforementioned nitrile rubber may have the aforementioned bound acrylonitrile content within a range from 40 to 51% by weight.

In accordance with this configuration, the bound acrylonitrile content within the aforementioned range provides more enhanced physical properties of the nitrile rubber. Hence, this provides further enhanced reliability of the refrigerant compressor.

Further, in the refrigerant compressor of the aforementioned configuration, the aforementioned refrigerant may be hydro fluorocarbon (HFC)-based refrigerant or a mixed refrigerant containing this HFC-based refrigerant, and the aforementioned lubricating oil may be at least one selected from the group consisting of ester oil, alkylbenzene oil, polyvinyl ether and polyalkylene glycol.

In accordance with this configuration, when the nitrile rubber satisfies the aforementioned conditions 1 to 3, reliability of the refrigerant compressor can be further particularly enhanced.

Further, in the refrigerant compressor of the aforementioned configuration, the aforementioned nitrile rubber may be vulcanized by peroxide vulcanization.

In accordance with this configuration, the nitrile rubber further satisfies the Condition 4: the peroxide vulcanization, in addition to satisfying the aforementioned Conditions 1 to 3. Therefore, deterioration in the quality of the internal member is suppressed even if the internal member is in contact with, for example, a hydrocarbon-based refrigerant. As a result, the reliability of the sealed refrigerant compressor can be further enhanced.

Further, in the refrigerant compressor of the aforementioned configuration, the aforementioned refrigerant may be a hydrocarbon-based refrigerant of at least one of R600a and R290 or a mixed refrigerant containing this hydrocarbon-based refrigerant, and the aforementioned lubricating oil may be at least one selected from the group consisting of mineral oil, ester oil, alkylbenzene oil, polyvinyl ether and polyalkylene glycol.

In accordance with this configuration, the reliability of the refrigerant compressor can be further enhanced, particularly when the nitrile rubber satisfies the aforementioned Conditions 1 to 4.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Throughout the drawings, the same or corresponding components are designated by the same reference symbols, and will not be described repetitively.

Embodiment 1 Example of Configuration of Refrigerant Compressor

As shown in the cross-sectional view of FIG. 1 and the longitudinal sectional view of FIG. 2, a refrigerant compressor 100 according to the present embodiment comprises a sealed container 10, an electric element 20, and a compression element 30.

The sealed container 10 is a sealed casing, which accommodates the electric element 20 and the compression element 30 therein, and is capable of retaining lubricating oil 11 in the bottom section thereof. In the present embodiment, this lubricating oil 11 exhibits viscosity within the range from VG3 to VG22, and preferably within the range from VG5 to VG22 according to the International Organization for Standardization (ISO) viscosity classification. Further, the inside of the sealed container 10 is communicated with the outside thereof through a suction pipe 40.

While the specific kind of the lubricating oil 11 is not particularly limited, at least one oil material selected from the group consisting of ester oil, alkylbenzene oil, polyvinyl ether and polyalkylene glycol is preferably employed in the present invention. One of these oil materials may be employed alone as the lubricating oil 11, or a mixture prepared by suitably combining two or more kinds of these oil materials may be employed as the lubricating oil 11.

In general, the viscosity of the lubricating oil 11 employed in the refrigerant compressor 100 can be suitably adjusted by blending oil materials having different viscosities. Therefore, two or more kinds of the aforementioned oil materials may also be blended in the present invention to achieve the adjusted viscosity of the lubricating oil 11 so that it falls into the range from VG3 to VG22. Alternatively, only a single oil material having a viscosity within the range from VG3 to VG22 may be employed as the lubricating oil 11.

The electric element 20 is composed of at least a stator 21 and a rotor 22 to rotatably actuate the compression element 30. The compression element 30 is assembled integrally with the electric element 20, and comprises a cylinder block 31, a piston 32 and a suction muffler 33. The cylinder block 31 is provided so as to form a cylindrical compression chamber 311. The piston 32 is provided so as to perform reciprocating motion within the inner space of the cylinder block 31. The suction muffler 33 has a muffling space 331 that is in communication with the compression chamber 311.

The suction muffler 33 further includes a suction port 332, through which a refrigerant can be introduced from the suction pipe 40. This suction port 332 is provided in a position where it does not overlap with the suction pipe 40 (a position outside of a projected position of the suction pipe 40) in a projection plan viewed from the direction along the central axis of the suction pipe 40. Further, a guide 333 made of nitrile rubber is provided at the suction port 332.

The guide 333 is fixed to the suction muffler 33 in a state that it projects out from the suction port 332. While a connecting section at which the suction pipe 40 and the sealed container 10 are connected to each other serves as an opening, through which the inside of the suction pipe 40 is in communication with the inside of the sealed container 10, the guide 333 is disposed in a position facing the opening of this suction pipe 40.

Hence, the refrigerant suctioned from the suction pipe 40 is capable of being introduced to the inside of the suction port 332 through this guide 333. Since the suction port 332 serves as an “introduction opening” of the refrigerant in the suction muffler 33, the refrigerant introduced to the inside of the suction muffler 33 is to be further introduced from the muffling space 331 of the suction muffler 33 to the compression chamber 311.

Here, the refrigerant compressor 100 shown in FIG. 1 and FIG. 2 has a standard configuration, and thus comprises various kinds of known mechanisms or members, in addition to the sealed container 10, the electric element 20, the compression element 30 and the suction pipe 40. Further, the specific configurations of the sealed container 10, the electric element 20, the compression element 30 and the suction pipe 40 are not particularly limited, and the known configurations are preferably employed.

In addition, the kind of the refrigerant available in the present invention is not particularly limited, and typical kinds of the refrigerant include: hydrocarbon-based refrigerants such as R600a, R290 and the like; HFC-based refrigerants such as R134a and the like; other known refrigerants that are available to be mixed with these refrigerants, and the like. One of these refrigerants may be employed alone, or a mixture prepared by suitably combining plural kinds of refrigerants may be employed. Here, R600a, R290, R134a and the like represent the serial number of the refrigerant defined in accordance with ISO817.

An example of an operation of the sealed refrigerant compressor 100 having the above-described configuration will be specifically described.

First of all, once an external power supply that is not shown in FIG. 1 and FIG. 2 is connected to the electric element 20 to supply an electric power to the electric element 20, the rotor 22 of this electric element 20 rotates. In association with the rotation of the rotor 22, the reciprocating motion of the piston 32 of the compression element 30 takes place for compression in the inner space of the cylinder block 31.

In the process for suctioning the refrigerant, the compression element 30 conducts operates as described above to provide reduced pressure in the compression chamber 311. This also reduces the internal pressure of the sealed container 10. While it is not shown in FIG. 1 and FIG. 2, an external refrigeration system is connected to the suction pipe 40, so that the refrigerant from this external refrigeration system passes through the suction pipe 40 to be once introduced in the sealed container 10, and then is released in front of the guide 333.

The lubricating oil 11 is scattered in the sealed container 10. Hence, a large amount of the refrigerant, together with the scattered lubricating oil 11, collides with the guide 333 facing the suction pipe 40. Or otherwise, the liquid refrigerant directly collides with the guide 333. Since the guide 333 is connected to the suction port 332 of the suction muffler 33, the refrigerant (and lubricating oil 11) having collided with the guide 333 is guided to the suction port 332 that is in a lower pressure, and is eventually suctioned into the suction muffler 33.

The refrigerant suctioned in the suction muffler 33 passes through the muffling space 331 of the suction muffler 33, and eventually is suctioned into the inside of the compression chamber 311 of the compression element 30. The refrigerant (and lubricating oil 11) suctioned in the compression chamber 311 is compressed in this compression chamber 311 by the reciprocating motion of the piston 32. The compressed refrigerant is to be discharged to the external refrigeration system again.

In this configuration, the guide 333 faces the suction pipe 40 in mutually proximity relation. Hence, the refrigerant introduced from the external refrigeration system is suctioned in the inside of the suction muffler 33 while its lower temperature is maintained, and then is compressed in the compression chamber 311. This increases a mass of the suctioned refrigerant (circulating rate of the refrigerant) in unit time. This results in increased efficiency of the refrigerant compressor 100, allowing enhanced refrigerating capability of the external refrigeration system.

[Internal Member Made of Nitrile Rubber]

In the present embodiment, the above-described guide 333 corresponds to an internal member made of nitrile rubber, which is provided in the inside of the refrigerant compressor 100.

While the rubber material employed for the guide 333 may be a known nitrile rubber, more specifically, nitrile butadiene rubber (NBR, copolymer of acrylonitrile and 1,3-butadiene), such a “nitrile rubber” in the present invention also contains: hydrogenated nitrile rubber, in which unsaturated bonds are hydrogenated; modified nitrile rubbers such as carboxylic group-modified nitrile rubber, silicone-modified nitrile rubber, maleic acid-modified nitrile rubber, hydroxyl group-modified nitrile rubber and the like, or hydrogenated products thereof, acrylonitrile-butadiene-isoprene copolymer, in which butadiene is partially substituted with isoprene; and the like.

In addition, in the present invention, the rubber material employed as the internal member of the guide 333 and the like may be made by using the nitrile rubber, and hence, the rubber material may contain a rubber material except the above-described nitrile rubber, and/or may contain various kinds of additives except phthalic ester. Therefore, the rubber material employed for the internal member may be a nitrile rubber composition that contains nitrile rubber as a major constituent. Hence, it is determined in the Specifications of the present application that the “internal member made of nitrile rubber” or the “guide 333 made of nitrile rubber” indicate the “internal member or guide 333, which is manufactured by using a nitrile rubber composition”.

Typical rubber materials other than the nitrile rubber include known rubbers such as natural rubber, ethylene propylene rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, butyl rubber, acrylic rubber and the like, though it is not particularly limited thereto.

In addition, typical additives include: inorganic fillers such as carbon, talc, clay, graphite and the like; processing aids such as palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, paraffin wax and the like; acid acceptors such as zinc oxide, magnesium oxide, hydrotalcite and the like; age resistors such as quinoline-based, amine-based or phenol-based age resistors; plasticizers other than phthalic ester, and the like, though it is not particularly limited thereto.

A vulcanizing agent is further employed in order to produce the nitrile rubber, and known vulcanizing agents may be employed as this vulcanizing agent. For example, the sulfur vulcanization employing sulfur or a sulfur-based compound as a vulcanizing agent, peroxide vulcanization employing an organic peroxide and the like as a vulcanizing agent, or the simultaneous use of the sulfur vulcanization and the peroxide vulcanization may be employed.

Specific kind of the organic peroxide employed in the peroxide vulcanization is not particularly limited, and typical organic peroxide includes, for example, alkyl-based peroxides, acyl-based peroxides, ketone peroxide-based peroxides, diacyl peroxide-based peroxides, hydro peroxide-based peroxides, dialkyl peroxide-based peroxides, peroxyketal-based peroxides, alkyl perester-based peroxides, percarbonate-based peroxides and the like. One of these peroxides may be employed alone, or suitable combination of two or more of these peroxides may be alternatively employed.

In addition, a vulcanizing accelerator may be used together with the vulcanizing agent in the manufacture of the nitrile rubber. While known vulcanizing accelerators may be used for this vulcanizing accelerator of the present invention, some kinds of organic compounds such as thiuram and the like are not employed as the vulcanizing accelerator in the present invention. This issue will be discussed later.

In addition to above, the above-described additives include compounds exhibiting vulcanizing acceleration effect (in other words, component that can be employed as vulcanizing accelerator) (for example, acid acceptors such as zinc oxide and the like; aliphatic acids (processing aid) such as stearic acid, oleic acid and the like). Hence, when these additives function as the vulcanizing accelerators, it is not necessary to add an extra vulcanizing accelerator.

In addition, while zinc oxide and the like, which is employed as an acid acceptor for the nitrile rubber, can also be employed as a vulcanizing agent for inorganic compound-based product, the vulcanizing agent employed in the present invention is limited to the above-described sulfur vulcanization agent or the peroxide vulcanization agent, and a vulcanization employing a vulcanizing agent other than these agents are not conducted in the present invention.

In addition, while the guide 333 is exemplified as the internal member made of the nitrile rubber in the present embodiment, the internal member of the present invention is not limited thereto. Any kind of member may be employed for the internal member in the present invention, so long as the member is a member that constitutes the electric element 20 and a member that constitutes the compression element 30, and also satisfies: (i) it is positioned in the sealed container 10 of the refrigerant compressor 100; (ii) it easily contacts the refrigerant or the lubricating oil 11, in which the refrigerant is dissolved; and (iii) it is a member made of a rubber or a member that can be produced by using a rubber material. Typical internal member except for the guide 333 may be, for example, a suction port 332 of the suction muffler 33. More specifically, if this suction port 332 is an opening member made of nitrile rubber, the member corresponds to the internal member in the present invention.

[Conditions Required for the Nitrile Rubber of the Present Invention]

The nitrile rubber employed in the internal member (guide 333) of the present invention satisfies: Condition 1: organic compound having carbon atom, which is capable of creating double bond with sulfur atom, nitrogen atom or carbon atom and is also capable of creating single bond with sulfur atom or nitrogen atom, is not used as a vulcanizing accelerator; and Condition 2: it is produced without containing phthalic ester. Further, the nitrile rubber of the present invention also satisfies: Condition 3: the bound acrylonitrile content of the nitrile rubber is within a range from 35 to 51% by weight.

In the present invention, “the organic compound having carbon atom, which is capable of creating double bond with sulfur atom, nitrogen atom or carbon atom and is also capable of creating single bond with sulfur atom or nitrogen atom” indicate compounds, which contains, in its molecular structure, chemical structures such as: —C(═S)—N; —C(═N)—N; —C(═C)—N; —C(═N)—S; —C(═S)—S; and the like. More specifically, typical examples of such compounds may include, for example, thiuram (having —C(═S)—N structure and —C(═S)—S structure), thiazole (having —C(═C)—N structure and —C(═N)—S structure), thiourea (having —C(═S)—N structure), dithiocarbamic acid (having —C(═S)—N structure and —C(═S)—S structure), and guanidine (having —C(═N)—N structure) and the like.

Here, the “dithiocarbamic acid” in the present invention includes compounds having the basic structure of dithiocarbamic acid (N—C(═S)—S). More specifically, various kinds of dithiocarbamates are included in the “dithiocarbamic acid” in the present invention. In addition, the “dithiocarbamic acid” in the present invention is not limited to “dithiocarbamic acid (dithiocarbamates) in the narrow sense” having two hydrogen atoms bound to one nitrogen atom (N) of the basic structure, and also includes compounds having the structure, in which organic group such as alkyl group and the like is bound to nitrogen atom.

According to the investigation of the present inventors, the use of the nitrile rubber that satisfies the aforementioned Conditions 1 to 3 provides enhanced oil resistance and chemical resistance of the nitrile rubber, without a need for containing phthalic ester. Therefore, even if a refrigerant becomes in contact with the internal member made of the nitrile rubber, the deterioration of the quality can be effectively avoided. Hence, the enhancement in efficiency can be achieved while maintaining the reliability of the refrigerant compressor 100.

Each of these conditions will be discussed. First of all, concerning the Condition 1, when the aforementioned vulcanizing accelerator is employed, generation of a deposit is found on the surface of the internal member made of the nitrile rubber, as shown in Examples as discussed later. It is considered that this deposit is a portion of the vulcanizing accelerator, which is bled out on the surface. Therefore, if the Condition 1 is not satisfied, the bleed out of the vulcanizing accelerator is caused on the internal member made of the nitrile rubber, leading to deteriorated quality of this internal member.

In the next, concerning the Condition 2, various kinds of problems derived from the presence of phthalic ester can be avoided by providing phthalic-ester-free configuration. Here, phthalic ester that is intended not to be contained in the nitrile rubber in the present invention indicates esters of ortho-phthalic acid and alcohols, and it is intended not to limited to only a specific compound but to be defined as comprehensive term. Typical phthalic ester includes dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, dinormal octyl phtalate, diisononyl phthalate, dinonyl phthalate, diisodecyl phthalate, butylbenzyl phthalate and the like, though it is not limited thereto.

Then, concerning the Condition 3, bound acrylonitrile content of the nitrile rubber of within a range from 35 to 51% by weight allows exhibiting enhanced physical properties that rubbers inherently have and providing increased amount of nitrile group (—CN) derived from acrylonitrile in rubber molecule. This provides a higher polarity of the nitrile rubber itself, so that the affinity for the refrigerant having lower polarity (or the lubricating oil 11 and the like containing the refrigerant) is decreased. As a result, excessive penetration of the refrigerant and the like in the internal member made of nitrile rubber can be suppressed.

On the other hand, if the bound acrylonitrile content of the nitrile rubber is lower than 35% by weight, the refrigerant or the like easily and excessively penetrates to the internal member, such that generation of a surface abnormality cannot be suppressed effectively. Meanwhile, if the bound acrylonitrile content of the nitrile rubber is higher than 51% by weight, the glass transition temperature of the nitrile rubber becomes equal to or higher than −10 degrees C. as shown in FIG. 3, such that, when an ambient temperature is decreased, brittleness of the rubber is increased, and thus it is impossible to maintain the characteristics that rubber inherently has. Therefore, it is sufficient that the content of the bound acrylonitrile is within a range from 35 to 51% by weight, and preferably the content may be within a range from 40 to 51% by weight, as illustrated in the examples.

In the next, the suppressing of the deterioration in the quality of the internal member which is associated with the nitrile rubber that satisfies the aforementioned Conditions 1 to 3 will be specifically described, with reference to an environment of the guide 333 within the sealed container 10 as an exemplary implementation.

While phthalic ester has been employed as the plasticizer of the nitrile rubber as described above, the use of phthalic ester is limited in recent years. Here, phthalic ester, which is added to the nitrile rubber, not only functions as a plasticizer, but also functions preventing penetration of the refrigerant. More specifically, when phthalic ester is added to the nitrile rubber, the phthalic ester is retained in the state of penetrating in interstitial spaces among rubber molecules of the nitrile rubber that is in the form of chain polymer molecule. Hence, even if the internal member is in contact with the refrigerant or the lubricating oil 11, in which a refrigerant is dissolved, the phthalic ester retained in the rubber molecule impedes the penetration of the refrigerant.

By comparison, when phthalic ester is not added to the nitrile rubber, there is no substance that fills interstitial spaces among rubber molecules. Thus, when the internal member is in contact with the refrigerant or the lubricating oil 11 (containing the refrigerant), the refrigerant easily penetrates in the rubber molecules. This results in a possibility of generating a deposit or of generating a material defect such as a blister and the like on the surface of the internal member made of the nitrile rubber. These surface abnormalities will cause deterioration in the quality of the internal member.

In particular, the guide 333 is provided in the position facing the suction pipe 40 so as to be closer to this suction pipe 40. Thus, when the refrigerant is introduced from the suction pipe 40, this refrigerant directly collides with the guide. Therefore, the guide 333 would be exposed to the refrigerant of a high concentration at a high frequency. Further, if the refrigerant in the liquid state collides with the guide 333, the refrigerant evaporates by the collision. Thus, the temperature of the guide 333 may be decreased due to the evaporation of the refrigerant.

By comparison, the internal member (for example, guide 333) in the present invention is produced by using the nitrile rubber that satisfies the above-described Conditions 1 to 3. Hence, even if the refrigerant is in contact with the internal member, the possibility of generating the surface abnormality in this internal member can be avoided, and sufficient physical properties that the rubber material inherently has can be exhibited even if the temperature of the internal member made of the nitrile rubber is decreased, because of satisfying the Condition 3 as illustrated in Examples shown below. This results in enhanced reliability of the refrigerant compressor. In particular, in the present embodiment, generation of a surface abnormality can be more effectively suppressed when the refrigerant is a HFC-based refrigerant such as R134a and the like, as shown in Examples described later.

Further in the present invention, it is preferable that the nitrile rubber may satisfy, in addition to the above Conditions 1 to 3: Additional Condition 1: Mooney viscosity at 100 degrees C. ML₁₊₄ is within a range from 50 to 150; and Additional Condition 2: hardness is within a range from 55 degrees to 80 degrees. Here, the Mooney viscosity of the nitrile rubber is measured on the basis of JISK6300-1 (JIS: Japanese Industrial Standards), and the hardness of the nitrile rubber is measured on the basis of JISK6253-3.

If the nitrile rubber satisfies the Additional Conditions 1 and 2, mechanical properties such as tensile strength and the like of this nitrile rubber are enhanced. Hence, if the internal member is the guide 333, easier manufacture and installation thereof can be achieved. Therefore, if the nitrile rubber satisfies the Conditions 1 to 3 and the Additional Conditions 1 and 2, the quality of the internal member can be enhanced, in addition to suppressing the generation of the surface abnormality. This results in further enhanced reliability of the refrigerant compressor 100.

Embodiment 2

While the nitrile rubber employed for the internal member of the refrigerant compressor 100 satisfies at least the aforementioned Conditions 1 to 3 in the aforementioned Embodiment 1, the present Embodiment 2 is configured such that the nitrile rubber additionally satisfies the Condition 4, in addition to the Conditions 1 to 3.

Here, the refrigerant compressor 100 employed in the present embodiment has the same configuration as that described in the aforementioned Embodiment 1 (see FIG. 1 and FIG. 2). In addition, the configuration of the nitrile rubber employed for the internal member is also the same as that described in the aforementioned Embodiment 1.

In the present embodiment, if the nitrile rubber satisfies the Condition 4: the nitrile rubber is vulcanized via the peroxide vulcanization, in addition to the aforementioned Conditions 1 to 3, in the case that the refrigerant is, or contains R600a and/or R290, the penetration of the refrigerant can be sufficiently suppressed.

In the aforementioned Embodiment 1, the available vulcanization of the nitrile rubber may be the sulfur vulcanization or the peroxide vulcanization. By comparison, the available vulcanization is specified to the peroxide vulcanization in accordance with the Condition 4 in the present embodiment. This can sufficiently suppress generation of a surface abnormality even if the hydrocarbon-based refrigerant penetrates to the nitrile rubber, as illustrated in Examples shown below.

More specifically, when the nitrile rubber that satisfies the Conditions 1 to 3 is in contact with a hydrocarbon-based solvent such as R600a, R290 and the like, a problem of generating roughened surface is caused, although generation of deposits and blisters can be suppressed, as illustrated in Examples shown below. In the present embodiment, the nitrile rubber satisfies the Condition 4 of the peroxide vulcanization to substantially prevent generation of a surface abnormality related to a roughened surface. Thus, the deterioration in the quality of the internal member made of the nitrile rubber (guide 333 and the like) can be effectively avoided, so that the refrigerant compressor 100 with enhanced reliability can be provided.

In addition, in the present embodiment, it is preferable that the nitrile rubber may satisfy, in addition to the above-described Conditions 1 to 4, the Additional Condition 1: Mooney viscosity ML₁₊₄ at 100 degrees C. is within a range from 50 to 150; and the Additional Condition 2: hardness is within a range from 55 degrees to 80 degrees. Therefore, if the nitrile rubber satisfies all of the Conditions 1 to 4 and the Additional Conditions 1 and 2, the quality of the internal member can be enhanced, in addition to effectively suppressing the penetration of the refrigerant, so that the reliability of the refrigerant compressor 100 can be further enhanced.

In addition, while ester oil, alkylbenzene oil, polyvinyl ether, and polyalkylene glycol are recited as the oil materials which can be preferably employed as the lubricating oil 11 in the aforementioned embodiment. In the present embodiment, mineral oil may also preferably be employed, in addition to these oil materials.

While the refrigerant compressor 100 exemplified in the aforementioned Embodiment 1 and the present Embodiment 2 is a reciprocating-type compressor as shown in FIG. 1 and FIG. 2, the compressor in the present invention is not limited thereto. It is needless to point out that the refrigerant compressor 100 available for the use in the present invention may be configured to have a sliding unit, a discharge valve and the like, and may be, for example, rotary-type, scroll-type, vibration-type or the like.

EXAMPLES

While the present invention will be more specifically described on the basis of Examples, Comparative examples and Prior art examples, the present invention is not limited thereto. It is apparent that the present invention may be modified, corrected and changed by a person having ordinary skills in the art without departing from the scope and the spirit of the present invention.

Prior Art Example 1

A conventional nitrile rubber, which contained phthalic ester, and was produced by being vulcanized via sulfur vulcanization and by employing thiuram as a vulcanizing accelerator, was used to prepare a sample specimen. The bound acrylonitrile content of this nitrile rubber was 32% by weight. This sample was accommodated in a sealed container together with R134a and polyol ester, and an aging treatment was conducted under the conditions of 125 degrees C. for two hours. Then, the surface of the sample specimen was observed by visual inspection. The result is shown in Table 1.

Comparative Example 1

A comparative nitrile rubber, which did not contain phthalic ester, and was produced by being vulcanized via sulfur vulcanization and by employing thiuram as a vulcanizing accelerator (bound acrylonitrile content of this nitrile rubber was 32% by weight), was used to prepare a sample specimen that is similar as prepared in Prior art example 1. An aging treatment was conducted under the similar conditions as employed in Prior art example 1. Then, the surface of the sample specimen was observed by visual inspection. The result is shown in Table 1.

Example 1

Nitrile rubber, which was produced by being vulcanized via sulfur vulcanization, and did not contain phthalic ester (Condition 2), and did not contain thiuram as a vulcanizing accelerator (Condition 1) and also exhibited bound acrylonitrile content of 40% by weight (Condition 3), was used to prepare a sample specimen that is similar as prepared in Prior art example 1. An aging treatment was conducted under the similar conditions as employed in Prior art example 1. Then, the surface of the sample specimen was observed by visual inspection. The result is shown in Table 1.

Example 2

Nitrile rubber that was similar as prepared in Example 1 except that vulcanization was conducted via peroxide vulcanization instead of sulfur vulcanization was used to prepare a sample specimen that was similar as prepared in Prior art example 1, and an aging treatment was conducted under the similar conditions as employed in Prior art example 1. Then, the surface of the sample specimen was observed by visual inspection. The result is shown in Table 1.

TABLE 1 Prior art Comparative example 1 example 1 Example 1 Example 2 condi- 1 vulcanizing Yes Yes No No tions accelerator 2 phthalic ester Yes No No No 3 bound 32% 32% 40% 40% acrylonitrile content 4 Vulcanizing sulfur sulfur sulfur peroxide process vulcani- vulcani- vulcani- vulcani- zation zation zation zation results Deposit No Yes No No

According to the result of Comparative example 1, a deposit was found on the surface of the sample specimen, even when the nitrile rubber that satisfies only the condition for containing no phthalic ester is employed. This deposit was analyzed with Fourier transform infrared spectrophotometer (FT-IR), and as shown in the IR spectrum of FIG. 4, a peak of sulfur-carbon double bond (C═S), which is unique to a vulcanizing accelerator, was found. Hence, it was found that a problem that portions of the vulcanizing accelerator (thiuram) are bled out on the surface, when only the condition for containing no phthalic ester is satisfied (only Condition 2).

By comparison, according to the results of examples 1 and 2, the use of the nitrile rubber, which did not contain phthalic ester (Condition 2), and did not use a vulcanizing accelerator (thiuram) (Condition 1) and also exhibited bound acrylonitrile content within a range from 35 to 51% by weight (Condition 3), provided the results, in which no deposit was found on the sample specimen for both vulcanizations of sulfur vulcanization and of peroxide vulcanization.

Therefore, on the basis of the results of Prior art example 1, Comparative example 1, and Examples 1 and 2, the phenomenon obtained when the nitrile rubber that satisfies the Conditions 1 to 3 is in contact with a HFC-based refrigerant (R134a) is considered as follows.

Any substance, which is capable of suppressing the penetration of the refrigerant in the interstitial spaces among rubber molecules, is not present in the sample specimen prepared by employing the nitrile rubber that does not contain phthalic ester (Comparative example 1). In particular, polyol ester, in which R134a is dissolved, exhibits reduced viscosity due to the presence of the dissolved R134a, so that such a polyol ester easily penetrates in the interstitial spaces among rubber molecules. Hence, a portion of the vulcanizing accelerator, which preliminarily exists in the interstitial spaces among rubber molecules, is pushed out onto the surface by R134a or polyol ester penetrating in the interstitial spaces among rubber molecules. It is considered that this results in the deposit on the surface of the sample specimen made of the nitrile rubber.

By comparison, no vulcanizing accelerator is pushed out on the surface of the nitrile rubber in the sample specimens employing the nitrile rubber that does not employ vulcanizing accelerator (Examples 1 and 2), and thus the deposit is not bled out.

In addition, no bleed out of the deposit was found in either of the cases where the vulcanization of the nitrile rubber was the sulfur vulcanization (Example 1) or the peroxide vulcanization (Example 2). In the case of the sulfur vulcanization, cross linkage is created in rubber molecules with bonds (—S—S—) between sulfur atoms. By comparison, in the case of the peroxide vulcanization, cross linkage is created in rubber molecules with bonds (—C—C—) between carbon atoms. Among these two kinds of cross linkages, the —C—C-bond provides higher bonding energy than the —S—S-bond. Hence, if the generation of the deposit on the surface could have been prevented in the nitrile rubber of Example 1 having —S—S-bond cross linkage, such prevention would be effective in the nitrile rubber of Example 2 having —C—C-bond cross linkage.

Prior Art Example 2

A conventional nitrile rubber, which contained phthalic ester, and was produced by being vulcanized via sulfur vulcanization and by employing thiuram as a vulcanizing accelerator, was used to prepare a sample specimen. The bound acrylonitrile content of this nitrile rubber was 32% by weight. This sample was accommodated in a sealed container together with R600a, and an aging treatment was conducted under the conditions of 125 degrees C. for two hours. Then, the surface of the sample specimen was observed by visual inspection. The result is shown in Table 2.

Comparative Example 2

A comparative nitrile rubber, which did not contain phthalic ester, and was produced by being vulcanized via sulfur vulcanization and by employing thiuram as a vulcanizing accelerator (bound acrylonitrile content of this nitrile rubber was 32% by weight), was used to prepare a sample specimen that was similar as prepared in Prior art example 1. An aging treatment was conducted under the similar conditions as employed in Prior art example 2. Then, the surface of the sample specimen was observed by visual inspection. The result is shown in Table 2.

Comparative Example 3

A sample specimen was produced similarly as in Comparative example 2, except that the bound acrylonitrile content of the nitrile rubber was provided to be 40% by weight. An aging treatment was conducted under the similar conditions as employed in Prior art example 2. Then, the surface of the sample specimen was observed by visual inspection. The result is shown in Table 2.

Comparative Example 4

A sample specimen was produced similarly as in Comparative example 3, except that no vulcanizing accelerator was employed in the vulcanization for the nitrile rubber. An aging treatment was conducted under the similar conditions as employed in Prior art example 2. Then, the surface of the sample specimen was observed by visual inspection. The result is shown in Table 2.

Example 3

Nitrile rubber, which did not contain phthalic ester (Condition 2), and did not contain thiuram as a vulcanizing accelerator (Condition 1), also exhibited bound acrylonitrile content of 40% by weight (Condition 3), and the vulcanization via the peroxide vulcanization was conducted (Condition 4), was used to prepare a sample specimen that is similar as prepared in Prior art example 2. An aging treatment was conducted under the similar conditions as employed in Prior art example 2. Then, the surface of the sample specimen was observed by visual inspection. The result is shown in Table 2.

Example 4

A sample specimen was produced similarly as in Example 2, except that the bound acrylonitrile content of the nitrile rubber was 51% by weight. An aging treatment was conducted under the similar conditions as employed in Prior art example 2. Then, the surface of the sample specimen was observed by visual inspection. The result is shown in Table 2.

TABLE 2 Prior art Comparative Comparative Comparative example 2 example 2 example 3 example 4 Example 3 Example 4 condi- 1 vulcanizing Yes Yes Yes No No No tions accelerator 2 phthalic ester Yes No No No No No 3 bound 32% 32% 40% 40% 40% 51% acrylonitrile content 4 Vulcanizing sulfur sulfur sulfur sulfur peroxide peroxide process vulcani- vulcani- vulcani- vulcani- vulcani- vulcani- zation zation zation zation zation zation results blister Yes Yes No No No No deposit No Yes Yes No No No roughened No No No Yes No No surface

It is clear from the results of Prior art example 2 and Comparative example 2 that, even if R600a was adopted instead of R134a and polyol ester, as the medium, to which the sample specimen of the nitrile rubber was exposed, the use of the nitrile rubber satisfying only the condition of containing no phthalic ester caused the deposits found on the surface of the sample specimen and also caused the generation of the blister.

This deposit on the sample specimen was analyzed with FT-IR, and as shown in the IR spectrum of FIG. 5, a peak of sulfur-carbon double bond (C═S), which is unique to a vulcanizing accelerator, was found. Hence, it was found that a problem that a portion of the vulcanizing accelerator (thiuram) was bled out on the surface occurred, similarly as the results of Comparative example 1, when only the condition for contain no phthalic ester is satisfied (only Condition 2).

In the next, according to the result of Comparative example 3, although a blister was not found, a deposit was found on the surface of the sample specimen. Hence, it is considered that the generation of the deposit cannot be effectively avoided by employing only the condition, in which the bound acrylonitrile content of the nitrile rubber is increased from 32% by weight to 40% by weight (Conditions 2 and 3). In the next, according to the result of Comparative example 4, although generation of a deposit was avoided by satisfying the condition for using no vulcanizing accelerator (thiuram) (Conditions 1 to 3), the roughened surface was found as new surface abnormality.

Here, it was clarified according to the comparison of the results of Comparative examples 2 to 4 that the bleeding-out of the deposit can be avoided by containing no phthalic ester (Condition 2) and employing no vulcanizing accelerator (Condition 1), and that generation of a blister can be prevented by increasing the bound acrylonitrile content of the nitrile rubber.

When the bound acrylonitrile content is increased, amount of nitrile group (—CN) derived from acrylonitrile in rubber molecule of the nitrile rubber is increased. Since nitrile group has a polarity, polarity of the entire molecule of the nitrile rubber is enhanced. On the other hand, R600a is a hydrocarbon-based refrigerant and thus exhibits lower polarity. Thus, if the polarity of the nitrile rubber is relatively high, the penetration of R600a into the nitrile rubber material is effectively suppressed. This can substantially prevent the generation of the blister.

By comparison, it was clarified according to the results of Examples 3 and 4 that none of the blister, the deposit and the roughened surface was found when the peroxide vulcanization was employed for the vulcanization of the nitrile rubber instead of the sulfur vulcanization (Conditions 1 to 4).

When the sulfur vulcanization is adopted for vulcanizing the nitrile rubber, oil resistance of the nitrile rubber is reduced unless a vulcanizing accelerator such as thiuram and the like is employed. If the oil resistance is reduced, a roughened surface is easily generated by being in contact with a hydrocarbon-based refrigerant such as R600a and the like. By comparison, the peroxide vulcanization is employed for vulcanizing the nitrile rubber in Examples 3 and 4. As described above, cross linkage is created with bonds (—S—S—) between sulfur atoms in the case of the sulfur vulcanization, while cross linkage is created with bonds (—C—C—) between carbon atoms in the case of the peroxide vulcanization. Among these two kinds of cross linkages, the —C—C-bond provides higher bonding energy than the —S—S-bond. Hence, a roughened surface of the nitrile rubber can be substantially prevented in Examples 3 and 4.

Numeral modifications and alternative embodiments of the present invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, the description is to be construed as illustrative only, and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and/or function may be varied substantially without departing from the spirit of the invention.

As described above, the refrigerant compressor with enhanced reliability can be provided according to the present invention, and therefore, the present invention can be widely applied to equipments employing refrigerating cycle. 

What is claimed is:
 1. A refrigerant compressor which reserves a lubricating oil having a viscosity of VG3 to VG22 in a sealed container and accommodates an electric element and a compression element that is actuated by the electric element to compress the refrigerant, wherein at least one of members constituting said electric element and members constituting said compression element is made of a rubber material, and wherein the rubber material is nitrile rubber, in which: bound acrylonitrile content is within a range of 35 to 51% by weight; organic compound having carbon atom, which is capable of creating double bond with sulfur atom, nitrogen atom or carbon atom and is also capable of creating single bond with sulfur atom or nitrogen atom, is not used as a vulcanizing accelerator in a process for creating cross-linkage; and no phthalic ester is contained.
 2. The refrigerant compressor according to claim 1, wherein said nitrile rubber exhibits Mooney viscosity ML₁₊₄ at 100 degrees C. of within a range from 50 to 150 and a hardness of within a range from 55 degrees to 80 degrees.
 3. The refrigerant compressor according to claim 2, wherein said nitrile rubber has said bound acrylonitrile content within a range from 40 to 51% by weight.
 4. The refrigerant compressor according to claim 1, wherein said refrigerant is hydrofluorocarbon (HFC)-based refrigerant or a mixed refrigerant containing the HFC-based refrigerant, and said lubricating oil is at least one selected from the group consisting of ester oil, alkylbenzene oil, polyvinyl ether and polyalkylene glycol.
 5. The refrigerant compressor according to claim 1, wherein said nitrile rubber is vulcanized by peroxide vulcanization.
 6. The refrigerant compressor according to claim 5, wherein said refrigerant is a hydrocarbon-based refrigerant of at least one of R600a and R290 or a mixed refrigerant containing the hydrocarbon-based refrigerant, and said lubricating oil is at least one selected from the group consisting of mineral oil, ester oil, alkylbenzene oil, polyvinyl ether and polyalkylene glycol. 